Smoking accelerates normal brain ageing in ways that can impair thinking skills such as planning, decision-making and problem-solving.
The good news is that it might be possible to reverse the harmful effects by giving up the habit, even late in life, scientists say.
Researchers analysed magnetic resonance imaging brain scan data on 504 men and women with an average age of 73.
Around half the participants were former or current smokers while the rest had totally avoided tobacco.
The findings showed that smoking appeared to increase the rate at which the outer layer of the brain, or cerebral cortex, thins with age.
This is the part of the brain linked to many higher functions, and plays a key role in memory, attention, language and awareness.
Lead scientist Professor Ian Deary, director of the centre for cognitive ageing at the University of Edinburgh, said: “It is important to know what is associated with brain health in older age and our study shows that the rate of smoking-related thinning to the brain is approximately twice the rate observed in previous, smaller studies.
“However, at the same time, our study also suggests that stopping smoking might allow the brain’s cortex to recover some of its thickness, though we need to conduct further studies to test this.”
Study participants who had given up smoking some time ago seemed to have a thicker cerebral cortex than more recent quitters, suggesting that they had experienced some degree of recovery.
The research, published in the journal Molecular Psychiatry, is part of The Disconnected Mind, a larger project investigating brain ageing funded by Age UK.